Design Of The PH Control System For The Wastewater Treatment Based On STM32 Micro-Controller

With the development of industry and the increasing of urban population, the wastewater treatment is being given more and more attention. For example, in chemical industry (pharmacy, zymolysis, paper making etc), wastewater treatment is very important to control liquor pH in a certain bound in these processes. But pH process has serious nonlinearity and hysteresis. There are many difficulties in detecting and controlling of pH value. The level of automation of the pH control system in China relatively falls behind its industrial production. Research and development of automatic system with good control effects and easy realization has much practical meaning.The most of apparatus used in pH process controlling are half-roboticized at present. There are several disadvantages in control process. This article put forward a new auto-control scheme for a pH process, using control theories and computers technology. First, this article makes a particular analysis for pH process and modeling, and finds out the characteristics of a pH process, the reasons for the difficult problems of controlling and the actuality of modeling for pH process. Secondly, it makes a study on the nonlinear problems of pH process and the methods of pH process controlling, and makes a more rational models for pH process. In this thesis, basing on the requests of the control system for pH value in wastewater treatment, a kind of variable gain PID controller for pH process is designed, in which the STM32 as its key part of processor is used. It accomplishes the data acquisition of pH value, the algorithm of variable gain PID control, the on-line controller and the serial communication with the monitor computer.The schemes of control system for the pH process in wastewater treatment based on variable gain PID control algorithm of separate-segment improve the precision and stability in control process. It is a beneficial attempt to apply advanced control method to solve practical industry problem. The design of the system which has advantages such as reasonable structure, low cost and strong practicability, satisfies the requirements of the automatic control for the pH process in wastewater treatment.